The wireless industrial switching system can be used to switch on or off four devices that are connected to the system. When these devices are switched on or off the status is shown on the control panel. This status shown is not a mere reflection of which switch has been pressed on the control panel, but is the feedback of the base unit to which the devices to be switched are connected. When a particular device is switched on, it draws current which is sensed and the status of the device is sent back to the control unit. Thus the status would be cent percent correct. The system also has a built in alarm for RF link failure.
The brief set up and description of the system is as under. There are two main units –first is the base or switching unit to which the devices to be switched are connected. This section has two ways radio link connected to the other unit which is the command or the control unit. The command or the control unit has four switches on the front panel with which devices can be controlled. Each switch has a corresponding LED aside it which shows the status of the device that is controlled by that particular switch.
2.1 Basic Block Diagrams
In this Project we are using Microcontroller AT89S52; it has advanced internal RAM, Timer and Counter then 89C51. It is in System Programmable 8K Byte of Flash Memory etc.
Components
3.1 Component List:
· Microcontroller IC 89S52
· HT12E(Encoder) IC, HT12D(Decoder) IC
· Capacitors(10µF, 100µF, 22pF, 2200µF)
· Resistors(100?, 100k?, 1k?, 10k?, 2k2?, 4k7?, 1M?)
· Relay(200V)
· Transistor BC 547
· Power Supply(12-0-12V/1A X’mer, 12-0-12V/500mA X’mer)
· Crystals Oscillator (12 MHz)
· IN4007, IN4148 Diode
· 7805 IC
· Rf Transmitter/Receiver (433MHz/315MHz)
· Simple switches
· LED
Circuit Diagrams
4.1 Circuit Diagram:
Fig.- Circuit Diagram of Switching unit
Fig.- Circuit Diagram of Control unit
Working
4.2 Working
The brief set up and description of the system is as under. There are two main units – first is the base unit to which the devices to be switched are connected. This section has two ways radio link connected to the other unit which is the command or the control unit. The command or the control unit has four switches on the front panel with which devices can be controlled. Each switch has a corresponding LED aside it which shows the status of the device that is controlled by that particular switch. For better understanding of the system it can be divided into following parts:
Base & Control Unit: –
The main sub sections of the base unit & control unit are as under:
- The rf receiver 1 section
- The decoder 1 section
- The main controller section
- The relay driver section
- The feedback encoder 2 section
- The relay based mains switching section
- The rf transmitter 1 and receiver 2 section
- The status display section
- The power supply section
The RF Receiver 1 Section
1. The RF Receiver 1 Section:
This section is what receives the data from the control unit about switching on or off a certain device. All the receivers and transmitters used in the system are of same type. They are given numbers due to the fact that a full duplex mode of communication has been realized in the working of the system. The first part of the link which comprises of receiver 1 at the base unit and transmitter 1 at the control and command unit is used to send and receive commands from the control unit to the base unit.
The second link which comprises of the rf transmitter 2 which is housed at the base unit and the rf receiver 2 which is stationed at the control unit is used to transmit and receive the status of the devices from the base unit to the control unit. Both the pairs utilize readymade transmitter-receiver modules that communicate in the ISM (industrial, scientific and medical band) which is a license free band. Both the pairs utilize ASK type of modulation. The pairs utilized are tailor made for digital serial communication and are compatible with TTL signal levels.
The output of the receiver 1 is fed to the decoder one; the transmitter 2 is fed data from the output of encoder 2. In the same way at the control unit the receiver 2 is feeds the input of the decoder 2 whereas the transmitter 1 is fed from the output of encoder 1. The rf pair has a maximum range of about 100m in constricted environs whereas in open environs it would permit a communication range of 300 to 500 m.
The Decoder 1 Section
2. The Decoder 1 Section:
The main task of the decoder is to convert the encoded serial data stream obtained from the rf receiver in to parallel form. The decoder that has been utilized is the HT12D chip from Holtek semiconductors. This chip is manufactured specially for remote control applications. The decoder has four data out lines, on VT signal out which is called the valid transmission signal and eight address inputs.
The address inputs are very important and are provided on the chip for authentication purposes. As soon as the chip receives a serial data packet from the receiver, it separates the address field from it. This address is compared with that physically set on the decoder chip. If the address is found to be identical then the VT output is taken high and the data received is output on the four data lines.
On the other hand if the address does not match, the entire packet is simply discarded. The addresses on the encoder 1 are matching to that on the decoder 1 and the addresses on the decoder 2 is matching to that on the encoder 2. Thus there cannot be any possibility of crosstalk between the two channels. The output of the decoder 1 is fed to the port 1 of the microcontroller for further processing.
The Main Controller Section
3. The Main Controller Section:
The main controller section: The controller used here is the 89S52 belonging to the 8051 family. This microcontroller has a classic 8051 core but has much advancement. The chip has an inbuilt 8kB flash ROM so that it can be programmed easily many times. This controller also boasts a RAM of 256 bytes. The programming voltage of this chip is also +5V which makes it quite easy to program and even giving it in system programming capability.
The use of the micro controller has simplified the circuit to a great extent. This circuit would have even been possible to construct using discrete components/ digital ICs but it would have been very complicated and difficult to implement. The usage of the micro controller also allows for further advancement of the project with ease at any date. The microcontroller has been connected in standard fashion. Its pin 9 has been connected to the power on reset network. It also has a push to on switch for manual reset. The controller has been furnished with a 12MHz crystal as a source of clock pulses. The four data out pins of the decoder 1 are directly connected to the lower nibble of the port 1. The VT terminal has also been utilized to interrupt the controller.
As the architecture of the controller does not allow interrupts which are low to high, the VT signal is applied to the controller after inverted by a single transistor. The software installed in the controller is such that whenever an interrupt arrives at the controller, it reads the data on the lower nibble of the port 1. After that the output port pin corresponding to that data is complemented, that is, 0 is converted to 1 and 1 is converted to 0. This will reflect in switching on or off a corresponding device.
The relay driver section: a bank of four relays has to be driven from the outputs of the controller. As the relays do demand quite a large amount of current and the controller is only capable of delivering a meager amount of current. Thus drivers are mandatory. Here we have implemented a ULN2803 Darlington driver chip as the driver. This chip has eight high gain transistor Darlington pairs inside it which can drive loads up to 500 mA.
The driver transistors also have inbuilt freewheeling diodes so that they can directly drive large inductive loads. The outputs of these drivers are used to drive relays.
Inductor 2 Section
4. The Inductor 2 section:
This section is the encoder that is matching with the decoder chip HT12D. This chip is named the HT12E which is also from Holtek Semiconductors. The address settings of the encoder are set according to the settings on the decoder at the command unit end. The four data lines are directly connected to the collectors of the driver chip. Thus when a particular driver is enabled, its collector goes low, taking with it the data line connected to that collector. To prevent the +12V level from reaching the encoder input, four diodes have been used in the connection.
The TE or the transmit enable pin is also permanently connected to ground so that the encoder continuously keeps on transmitting. The output of the encoder is fed to the data input of the rf transmitter 2.
RF Transmitter 2 & Relay Based Main Switching Section
5. The RF Transmitter 2:
The rf transmitter 2 is the same unit that was explained in the previous sections. It transmits the serial data from the encoder to the remote control and command unit.
6. The Relay Based Mains Switching Section:
As the devices that are to be switched on are of course going to be ac operated. Thus some form of ac switching arrangement would be required. This has been realized in the project with the help of four electromagnetic relays. The use of relays ensures sufficient isolation between the dc control circuit and the ac load that is being switched. The relays used here are 12V pcb mount type having a resistance between 150 to 200 ohms which would thus require about 65mA of current to drive it. The loads are connected to the normally open contacts of the relay so that the devices will be switched on when the relays are energized.
The status display and key pad section: this section lets the user see the status of the remote loads that are connected to the base unit. As explained earlier, the status is sent from the base unit to the command and control unit by the encoder 2– rf transmitter2-rf receiver2-decoder 2 link.
The status display LEDs have been directly connected to the output of decoder 2 as it capable of driving the LEDs directly. The decoder itself also drives the warning buzzer via a driver. This buzzer would start buzzing whenever the VT signals from the decoder disappears indicating a break in the rf link.
The key pad has only four switches, one for each load to be controlled. Of course by the merit of four data lines that the encoder has it is easily possible to control 16 loads without much alteration in the hardware. The switches are directly connected to the data input lines of the encoder 1.
Power Supply Section
7. The Power Supply Section:
The system requires two different power supplies, one for the base unit and the other for the command and control unit. The base unit current requirement is quite hefty taking into consideration the current requirement of the controller and the four relays plus the additional hardware.
The power supply at the base unit thus has a 12-0-12V /1A transformer. As the unit requires two different supplies 12V and +5V a 7805 regulator chip is utilized. The 12V supply is taken from the rectifier directly as it does not require any regulation.
On the other hand the command and control unit has quite a modest current requirement thus only 12-0-12V/500mA transformer is necessary along with a 7805 regulator for the 5V supply required.
Characteristics & Applications
Characteristics:
There are many of such Characteristics present but this on off devices or equipment have to be done by wireless only so it have to follow some characteristics. Because of the strict requirements of automation scenarios a suitable wireless solution should fulfill at least some characteristics:
· Resilient and reliable;
· Immune to interference from other radio sources;
· Multiple-access
· Priority capable
· Broadband
· Scalable
· Secure
Application:
- This module can be used in any small or big architectural company.
- We can connect many of devices simultaneously with each other & also do on off them automatically or manually.
- We do on off following devices:
Lathe Machines
CNC Machines
Electronics Hardware
Electrical Equipment etc.
Codes
Codes
C code:
#include<p89v51rx2.h>
sbit one = P1^0;
sbit two = P1^1;
sbit three = P1^2;
sbit four = P1^3;
sbit OP1 = P2^0;
sbit OP2 = P2^1;
sbit OP3 = P2^2;
sbit OP4 = P2^3;
//==============================================================
void main(void)
{
TCON = 0x01;
IE = 0x81;
P1 = 0xff;
P2 = 0x00;
while(1)
{
}
}
//==================================================
void EINT0(void) interrupt 0
{
if(one == 1)
{
if(two == 1)
{
if(three == 1)
{
if(four == 1)
{
return;
}
else
{
OP4 = ~OP4;
}
}
else
{
OP3 = ~OP3;
}
}
else
{
OP2 = ~OP2;
}
}
else
{
OP1 = ~OP1;
}
}
Assembly Code:
org 0000h
ljmp main
org 0003h
ljmp in0
org 0030h
main: mov sp,#0fh
mov ie,#10000001b
setb tcon.0
mov p1,#0ffh
mov p2,#00h
here: sjmp here
in0: jb p1.0,two
cpl p2.0
two: jb p1.1,tre
cpl p2.1
tre: jb p1.2,four
cpl p2.2
four: jb p1.3,next
cpl p2.3
next: reti
end
Project Source Code
Project Source Code
###
sbit one = P1^0; sbit two = P1^1; sbit three = P1^2; sbit four = P1^3; sbit OP1 = P2^0; sbit OP2 = P2^1; sbit OP3 = P2^2; sbit OP4 = P2^3; //============================================================== void main(void) { TCON = 0x01; IE = 0x81; P1 = 0xff; P2 = 0x00; while(1) { } } //================================================== void EINT0(void) interrupt 0 { if(one == 1) { if(two == 1) { if(three == 1) { if(four == 1) { return; } else { OP4 = ~OP4; } } else { OP3 = ~OP3; } } else { OP2 = ~OP2; } } else { OP1 = ~OP1; } } Assembly Code: org 0000h ljmp main org 0003h ljmp in0 org 0030h main: mov sp,#0fh mov ie,#10000001b setb tcon.0 mov p1,#0ffh mov p2,#00h here: sjmp here in0: jb p1.0,two cpl p2.0 two: jb p1.1,tre cpl p2.1 tre: jb p1.2,four cpl p2.2 four: jb p1.3,next cpl p2.3 next: reti end
###
Circuit Diagrams
Filed Under: Electronic Projects
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